Field of the Invention
The invention relates to a method and to a device for processing a signal, in particular for recognizing an irregularity in the signal.
An irregularity in a signal, in particular an analog measurement signal, can in practice often be recognized or ascertained only with difficulty. This is particularly so if the irregularity is very small in comparison with the signal. As a rule, the signal must to this end be converted in a suitable way. The term irregularity is defined, in this context, as an interference in the signal, a superimposed interference signal, or an irregularity due to an effect on or distortion of the signal. The signal itself may in this case be present as analog or digital information.
One known approach for converting the signal to form a complex time signal is represented by the Hilbert transform. The Hilbert transform is used, for example, for modeling in data technology to form a so-called analytical signal.
Reference is had, in this regard to an article by Skerl et al., "Wigner-Verteilung als Werkzeug zur Zeit-Frequenz-Analyse nichtstationarer Signale" [Wigner Distribution As A Tool For The Time-Frequency Analysis Of Non-Steady Signals], in tm--Technisches Messen 61 (1994) 1, pages 7-15. The method mentioned therein provides an interrelation between signals shifted relative to one another in autocorrelation fashion and their transformation.
A system for calculating the real and imaginary parts of an input signal is described in U.S. Pat. No. 4,984,188 to Kato. The two signal parts are then either treated to form a mean or, after forming a ratio, processed using the arctangent function. The object of that signal treatment is to obtain an interference-free signal.
A system for estimating the frequency of a signal is known from U.S. Pat. No. 4,983,906 to Hiller. The frequency analysis achieves phase-invariant evaluation of a signal by forming a normal and quadrature component, for example by applying the Hilbert transform. This is intended to permit improved frequency analysis.
German published patent application DE-37 06 865 A1 discloses a method in which complex-value time signals are produced by modulation with mutually orthogonal carriers. This is followed by forming an arctangent. The method is intended to achieve efficient determination of a bearing angle.